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Essential oils (EOs) are mixtures of volatile organic compounds that mediate plant interactions and are also appreciated for their biological properties in aromatic plants. However, the study of EOs in wild plants with biological activity has been neglected. Ipomoea murucoides is a wild species with allelopathic and insecticide activities; however, the climate factors associated with EOs and their role in intra- and interspecific interactions are still unknown. We investigated the effects of temperature, rain, and solar irradiance for two years on the EOs of I. murucoides and documented the effect of herbivory (without, <20%, >20%, and mechanical damage) on their composition. We evaluated the receptivity to possible infochemicals in conspecific and congeneric neighbors to I. murucoides plants exposed to methyl jasmonate (MeJA), herbivory by Ogdoecosta biannularis and without an elicitor. We measured the stomatal density and aperture in the second leaf generation of the neighbor plants. The year and herbivory >20% affected the composition of EOs. Nerolidol could be a biological marker for herbivory. We concluded that herbivory and rain irregularity contribute to EOs changing. The response in the stomatal density in plants not consumed by I. pauciflora but near I. murucoides under MeJA or herbivory gives evidence of interspecific plant–plant communication. [ABSTRACT FROM AUTHOR]

We quantified the effect of two cyclopoids, an invasive (Mesocyclops pehpeiensis) and a native (Mesocyclops longisetus curvatus) species on the population growth of the rotifers Brachionus havanaensis and Brachionus calyciflorus. We hypothesized that the invasive copepod would have a greater adverse effect on the test rotifers. The population growth of B. havanaensis was tested in the indirect presence of B. calyciflorus (used as prey for the predatory copepods), and the predatory copepods, M. pehpeiensis and M. longisetus curvatus. For B. calyciflorus the experimental design was as above except that we used B. havanaensis as prey. The test rotifers were separated from the competitors and predators by mesh cages placed in the experimental jars. Rotifer density and the egg ratios were quantified, followed by a daily medium change, until the population density declined. The population growth rate of B. havanaensis ranged between 0.26 and 0.30 day−1, while that of B. calyciflorus between 0.19 and 0.21 day−1. The presence of the invasive copepod had an adverse effect on the smaller (< 110 µm) B. havanaensis, but not on the larger (> 180 µm) B. calyciflorus. The results are discussed with emphasis on the differences in the indirect impact invasive and native predatory copepods. [ABSTRACT FROM AUTHOR]

For the freshwater phytoplankton Scenedesmus, morphological defense induced by infochemicals released from grazers (such as Daphnia) is considered to be a defensive strategy. In this study, we investigated the response of Scenedesmus obliquus to long-term repeated grazing infochemicals exposure, with two stimulation intervals (short period of 4 days and long period of 7 days per round). Results demonstrated that the defensive response of S. obliquus gradually degenerated with periodically repeated exposure to Daphnia infochemicals and the degeneration rate was positively correlated with stimulation frequency, that is, shorter intervals caused a faster decrease in average algal colony size. According to nonlinear regression fitting, a harmonic oscillator function with exponential attenuation could be applied to illustrate S. obliquus morph changes, with which the growth rate was positively correlated. Our study suggests that the optimal defensive colony size in S. obliquus might depend on trade-offs between its anti-grazing defense and other functions. This insight contributes to the understanding of algal inducible defense mechanism, serving as a complement to the optimal defense theory. Additionally, long-term periodic grazing threats without causing concrete damage may disrupt feedback mechanisms and real biomass loss is assumed to be an important precondition for sustaining enduring defensive phenotypes. [ABSTRACT FROM AUTHOR]

Essential oils (EOs) are mixtures of volatile organic compounds that mediate plant interactions and are also appreciated for their biological properties in aromatic plants. However, the study of EOs in wild plants with biological activity has been neglected. Ipomoea murucoides is a wild species with allelopathic and insecticide activities; however, the climate factors associated with EOs and their role in intra- and interspecific interactions are still unknown. We investigated the effects of temperature, rain, and solar irradiance for two years on the EOs of I. murucoides and documented the effect of herbivory (without, 20%, and mechanical damage) on their composition. We evaluated the receptivity to possible infochemicals in conspecific and congeneric neighbors to I. murucoides plants exposed to methyl jasmonate (MeJA), herbivory by Ogdoecosta biannularis and without an elicitor. We measured the stomatal density and aperture in the second leaf generation of the neighbor plants. The year and herbivory >20% affected the composition of EOs. Nerolidol could be a biological marker for herbivory. We concluded that herbivory and rain irregularity contribute to EOs changing. The response in the stomatal density in plants not consumed by I. pauciflora but near I. murucoides under MeJA or herbivory gives evidence of interspecific plant–plant communication.

Multisensory stimuli provide organisms with information to assess the threat present in the surroundings. Olfactory cues show dominance over other sensory modalities in the aquatic environment. The impact of chemical predator cues combined with experiences gained (learning) in species without previous contact is not fully understood. We investigated the foraging and shelter‐seeking behaviour of naïve and experienced marbled crayfish Procambarus virginalis juveniles in response to the chemical signals of pumpkinseed Lepomis gibbosus alone and in combination with alarm chemicals produced by preyed‐upon conspecifics. Naïve and experienced (previously exposed to pumpkinseed predation) juveniles were stocked in an arena with shelter and feed and exposed (1) to water from a tank containing a predator actively feeding on conspecifics, (2) water from a tank with predator only and (3) water only as control. Crayfish exposed to the combined stimuli avoided the inlet zone and gravitated to shelter zone of the arena to a greater extent than did those exposed to predator‐only cues and the control. Regardless of the treatment, experienced crayfish showed significantly reduced interest in feeding. Our findings imply that crayfish response to threat‐associated odours with the greatest potency when visual or tactile cues are present, while previous encounters with predators may make them more cautious. [ABSTRACT FROM AUTHOR]

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Simple Summary: Zelus renardii is one of the alien insects recently acclimatised to the Mediterranean basin. The trivial name "leafhopper assassin bug" preludes the reduviid prey preference. In the Mediterranean, Zelus renardii adapted to preying on vicarious indigenous species, including Philaenus spumarius (Hemiptera: Aphrophoridae), the European vector of Xylella fastidiosa. Reduviidae has several thoracic glands, pair or unpair, whose secretions may regulate adult insect behaviours, such as defence, alarm, and mating. Zelus renardii also possesses a pair of Brindley's glands, each consisting of about one hundred elements secerning in a reservoir with an outlet that opens at the thoracoabdominal limit. Stressful events elicit the production and secretion of a semiochemical bouquet, acting as alarm pheromones. This bouquet comprises 2-methyl-propanoic acid, 2-methyl-butanoic acid and 3-methyl-1-butanol as significant components, effectively repel conspecifics and suggest the role of Brindley's glands as alarm pheromone foci. Zelus renardii reduces the production of alarm pheromones and the chance of being detected by prey interacting with P. spumarius. Alternatively, the alarm pheromone could help the predator to mark its territory, avoiding interaction with a conspecific. Evidence of the ability of Philaenus spumarius to perceive and react to the predator's semiochemical would provide a further means to manage transmission and infection by Xylella fastidiosa. Alien species must adapt to new biogeographical regions to acclimatise and survive. We consider a species to have become invasive if it establishes negative interactions after acclimatisation. Xylella fastidiosa Wells, Raju et al., 1986 (XF) represents Italy's and Europe's most recent biological invasion. In Apulia (southern Italy), the XF-encountered Philaenus spumarius L. 1758 (Spittlebugs, Hemiptera: Auchenorrhyncha) can acquire and transmit the bacterium to Olea europaea L., 1753. The management of XF invasion involves various transmission control means, including inundative biological control using Zelus renardii (ZR) Kolenati, 1856 (Hemiptera: Reduviidae). ZR is an alien stenophagous predator of Xylella vectors, recently entered from the Nearctic and acclimated in Europe. Zelus spp. can secrete semiochemicals during interactions with conspecifics and prey, including volatile organic compounds (VOCs) that elicit conspecific defence behavioural responses. Our study describes ZR Brindley's glands, present in males and females of ZR, which can produce semiochemicals, eliciting conspecific behavioural responses. We scrutinised ZR secretion alone or interacting with P. spumarius. The ZR volatilome includes 2-methyl-propanoic acid, 2-methyl-butanoic acid, and 3-methyl-1-butanol, which are consistent for Z. renardii alone. Olfactometric tests show that these three VOCs, individually tested, generate an avoidance (alarm) response in Z. renardii. 3-Methyl-1-butanol elicited the highest significant repellence, followed by 2-methyl-butanoic and 2-methyl-propanoic acids. The concentrations of the VOCs of ZR decrease during the interaction with P. spumarius. We discuss the potential effects of VOC secretions on the interaction of Z. renardii with P. spumarius. [ABSTRACT FROM AUTHOR]

Coniferous trees of the genus Pinus (Pinaceae) are under continuous threats by numerous herbivorous insect species and pathogens attacking nearly all parts and tissues of the plants. To defend themselves, pine trees produce large amounts of oleoresin that is accumulated in a highly developed network of specialized resin ducts, which are distributed in the wood, bark, and needles. Such defense reactions in pines can be induced by the attack of herbivores. The banded pine weevil, Pissodes castaneus (De Geer, 1775) (Coleoptera, Curculionidae), is an important pest of Pinus in Brazil, where it has been an invasive species since 2001. The female lays its eggs under the tree bark of trees and the larvae feed in the phloem of the trunk and branches, interrupting the sap circulation and eventually causing its death. In the present study, we conducted detailed GC–MS analyses of volatiles emitted by twigs of Pinus taeda L. We analyzed how the attack by P. castaneus males and females affects the volatile pattern emitted by the twigs. When comparing volatiles produced by healthy plants and by female- and male-attacked P. taeda, qualitative and quantitative differences were detected, as the decreased production of limonene, germacrene D and (E)-caryophyllene and the increase of α-pinene. Laboratory bioassays showed that plants attacked by male and female P. castaneus were more attractive to the insects. Understanding about what compounds may attract or repel the insects may help in the development of more effective traps, as well as preventing stress to avoid infestation. [ABSTRACT FROM AUTHOR]

Abstract Multisensory stimuli provide organisms with information to assess the threat present in the surroundings. Olfactory cues show dominance over other sensory modalities in the aquatic environment. The impact of chemical predator cues combined with experiences gained (learning) in species without previous contact is not fully understood. We investigated the foraging and shelter‐seeking behaviour of naïve and experienced marbled crayfish Procambarus virginalis juveniles in response to the chemical signals of pumpkinseed Lepomis gibbosus alone and in combination with alarm chemicals produced by preyed‐upon conspecifics. Naïve and experienced (previously exposed to pumpkinseed predation) juveniles were stocked in an arena with shelter and feed and exposed (1) to water from a tank containing a predator actively feeding on conspecifics, (2) water from a tank with predator only and (3) water only as control. Crayfish exposed to the combined stimuli avoided the inlet zone and gravitated to shelter zone of the arena to a greater extent than did those exposed to predator‐only cues and the control. Regardless of the treatment, experienced crayfish showed significantly reduced interest in feeding. Our findings imply that crayfish response to threat‐associated odours with the greatest potency when visual or tactile cues are present, while previous encounters with predators may make them more cautious.

Parasitoids are important biological control agents for many agricultural pests. Mating and parasitizing hosts are the two most prominent behaviors of parasitoids and are essential for their reproduction and survival. Therefore, the identification of the infochemicals involved in mating and parasitizing is an important first step to understanding the chemical ecology of these species. In recent decades, state-of-the-art chemical analysis techniques, such as gas chromatographyelectroantennographic detection (GC-EAD), has resulted in the identification of an increasing number of infochemicals that regulate parasitoid behavior. Herbivore-induced plant volatiles (HIPVs) and host-derived kairomones are two major categories of chemical cues guiding host detection. Based on this, the concept of "tritrophic" (plant-pest-parasitoid) interactions has been developed, significantly deepening our understanding of the mechanisms underlying host identification by parasitoids. Identification of parasitoid sex pheromones has been challenging due to their small body size and the correspondingly small amounts of sex pheromones released. The sex pheromone communication mechanism in a parasitoid, Campoletis chlorideae, has recently been elucidated. The results indicate that sex pheromones can enhance the parasitizing capacity of parasitoids by facilitating mating. In this review we summarize the infochemicals that regulate parasitoid behaviors and discuss the prospects and challenges of applying these infochemicals to control insect pests. [ABSTRACT FROM AUTHOR]

Diverse ecologically important metabolites, such as allelochemicals, infochemicals and volatile organic chemicals, are involved in marine organismal interactions. Chemically mediated interactions between intra- and interspecific organisms can have a significant impact on community organization, population structure and ecosystem functioning. Advances in analytical techniques, microscopy and genomics are providing insights on the chemistry and functional roles of the metabolites involved in such interactions. This review highlights the targeted translational value of several marine chemical ecology-driven research studies and their impact on the sustainable discovery of novel therapeutic agents. These chemical ecology-based approaches include activated defense, allelochemicals arising from organismal interactions, spatio-temporal variations of allelochemicals and phylogeny-based approaches. In addition, innovative analytical techniques used in the mapping of surface metabolites as well as in metabolite translocation within marine holobionts are summarized. Chemical information related to the maintenance of the marine symbioses and biosyntheses of specialized compounds can be harnessed for biomedical applications, particularly in microbial fermentation and compound production. Furthermore, the impact of climate change on the chemical ecology of marine organisms—especially on the production, functionality and perception of allelochemicals—and its implications on drug discovery efforts will be presented. [ABSTRACT FROM AUTHOR]

We live in the information age, but we still do not fully understand how the surrounding nature exchanges, collects, and manages information—both at the ecosystem and cellular levels. Still, it is crucial to possess a dynamic and developing comprehension of the functioning of nature in order to understand the phenomena occurring in our ever-changing world. Sometimes we encounter an attitude that there is no need to investigate anything further, as everything has already been researched. This is a very dangerous attitude. Without information, we should not actually talk about the age of information, and it is worth reviewing some knowledge that is deeply ingrained in us from time to time. Occasionally, it is worth taking a step back and considering whether we ourselves may have become trapped in dogmas that may hinder our understanding. This presentation focuses on various aspects of understanding nature, starting from single-celled organisms and ending with ecosystems. The topics that will be discussed among others are (1) infochemicals (how do they actually affect the biota?); (2) the remarkable process of cellular computation (does this imply that cellular materials can show a primitive intelligence?); and (3) the ability of plants to influence wind patterns and bring in more moisture from the ocean (what will happen to us when we excessively deforest?).

The aim of this study was to explore whether the widespread zooplankter Daphnia magna is able to differentiate between the kairomones of planktivorous common bleak (Alburnus alburnus) and omnivorous black bullhead (Ameiurus melas). We expected different responses in some plastic defensive traits because the presence of a planktivorous and an omnivorous fish pose a different degree of threat to daphnids. Our mesocosm study showed that the size distribution of D. magna in the bleak treatment tended to differ from both black bullhead and control treatments, while there was no apparent difference between the latter two treatments. The eye diameter/body length ratio and tail spine/body length ratio of D. magna were highest in the bleak treatment, differing from both black bullhead and control treatments, and without any significant difference between the latter two treatments. We found that only bleak triggered detectable responses in D. magna, suggesting either that kairomones of the studied fish species could differ in their chemical composition, or that black bullhead may exude less kairomone than bleak. [ABSTRACT FROM AUTHOR]

Volatiles are important 'infochemicals' that play a crucial role in structuring life on our planet, fulfilling diverse functions in natural and artificial systems. Algae contribute significant quantities to the global budget of volatiles, but the ecological roles of aquatic volatiles are not well understood. In this review, we discuss the current knowledge of volatile compounds from freshwater and marine microalgae and marine macroalgae, with a focus on their ecological roles. We highlight the multiple reported functions of biogenic volatiles, ranging from intraspecific communication for reproduction, intra‐bloom signalling and antioxidant functions, to various interspecific signal exchanges that may allow herbivores to locate them and function in defence against competitors and predators. Beyond reviewing our current understanding, we specifically highlight major knowledge gaps and emerging questions for algal volatile research. These novel perspectives have the potential to improve our understanding of aquatic ecosystems and thus need to be addressed in future research. Filling these gaps and addressing these questions will facilitate humanity's efforts to exploit aquatic volatiles in various applications. [ABSTRACT FROM AUTHOR]

Chemical communication via infochemicals plays a pivotal role in ecological interactions, allowing organisms to sense their environment, locate predators, food, habitats, or mates. A growing number of studies suggest that climate change‐associated stressors can modify these chemically mediated interactions, causing info‐disruption that scales up to the ecosystem level. However, our understanding of the underlying mechanisms is scarce. Evidenced by a range of examples, we illustrate in this opinion piece that climate change affects different realms in similar patterns, from molecular to ecosystem‐wide levels. We assess the importance of different stressors for terrestrial, freshwater, and marine ecosystems and propose a systematic approach to address highlighted knowledge gaps and cross‐disciplinary research avenues. [ABSTRACT FROM AUTHOR]

Most biological diversity on Earth is contained within microbial communities. In the ocean, these communities dominate processes related to carbon fixation and nutrient recycling. Yet, specific factors that determine community composition and metabolic activity are difficult to resolve in complex microbial populations, complicating predictions of microbial processes in a changing ocean. Microbial metabolism generates small organic molecules that reflect both the biochemical and physiological diversity as well as the taxonomic specificity of these biological processes. These small molecules serve as the conduit for taxon-specific signaling and exchange. Here, we use liquid chromatography-mass spectrometry (LC-MS)-based metabolomics to taxonomically categorize 111 metabolites that include small molecules in central and secondary metabolism across 42 taxa representing numerically dominant and metabolically important lineages of microbial autotrophs and heterotrophs. Patterns in metabolite presence-absence broadly reflected taxonomic lineages. A subset of metabolites that includes osmolytes, sulfur-containing metabolites, sugars, and amino acid derivatives provided chemotaxonomic information among phytoplankton taxa. A variety of phytohormones and signaling molecules were predominantly found in the heterotrophic bacteria and archaea, expanding knowledge of metabolites implicated in modulating interactions between microbes. This chemotaxonomic inventory of marine microbial metabolites is a key step in deciphering metabolic networks that influence ocean biogeochemical cycles.

Alien species must adapt to new biogeographical regions to acclimatise and survive. We consider a species to have become invasive if it establishes negative interactions after acclimatisation. Xylella fastidiosa Wells, Raju et al., 1986 (XF) represents Italy’s and Europe’s most recent biological invasion. In Apulia (southern Italy), the XF-encountered Philaenus spumarius L. 1758 (Spittlebugs, Hemiptera: Auchenorrhyncha) can acquire and transmit the bacterium to Olea europaea L., 1753. The management of XF invasion involves various transmission control means, including inundative biological control using Zelus renardii (ZR) Kolenati, 1856 (Hemiptera: Reduviidae). ZR is an alien stenophagous predator of Xylella vectors, recently entered from the Nearctic and acclimated in Europe. Zelus spp. can secrete semiochemicals during interactions with conspecifics and prey, including volatile organic compounds (VOCs) that elicit conspecific defence behavioural responses. Our study describes ZR Brindley’s glands, present in males and females of ZR, which can produce semiochemicals, eliciting conspecific behavioural responses. We scrutinised ZR secretion alone or interacting with P. spumarius. The ZR volatilome includes 2-methyl-propanoic acid, 2-methyl-butanoic acid, and 3-methyl-1-butanol, which are consistent for Z. renardii alone. Olfactometric tests show that these three VOCs, individually tested, generate an avoidance (alarm) response in Z. renardii. 3-Methyl-1-butanol elicited the highest significant repellence, followed by 2-methyl-butanoic and 2-methyl-propanoic acids. The concentrations of the VOCs of ZR decrease during the interaction with P. spumarius. We discuss the potential effects of VOC secretions on the interaction of Z. renardii with P. spumarius.

Smell is a sensory modality that is rarely considered in birds, but evidence is mounting that olfaction is an important aspect of avian behaviour and ecology. The uropygial gland produces an odoriferous secretion (preen oil) that can differ seasonally and between the sexes. These differences are hypothesized to function in olfactory camouflage, i.e. minimizing detection by nest predators (olfactory crypsis hypothesis), and/or intraspecific olfactory communication, particularly during breeding (sex semiochemical hypothesis). However, evidence for seasonal and sex differences in preen oil is mixed, with some studies finding differences and others not, and direct evidence for the putative function(s) of seasonal variation and sex differences in preen oil remains limited. We conducted a systematic review of the evidence for such changes in preen oil chemical composition, finding seasonal differences in 95% of species (57/60 species in 35 studies) and sex differences in 47% of species (28/59 species in 46 studies). We then conducted phylogenetic comparative analyses using data from 59 bird species to evaluate evidence for both the olfactory crypsis and sex semiochemical hypotheses. Seasonal differences were more likely in the incubating than non‐incubating sex in ground‐nesting species, but were equally likely regardless of incubation strategy in non‐ground‐nesting species. This result supports the olfactory crypsis hypothesis, if ground nesters are more vulnerable to olfactorily searching predators than non‐ground nesters. Sex differences were more likely in species with uniparental than biparental incubation and during breeding than non‐breeding, consistent with both the olfactory crypsis and sex semiochemical hypotheses. At present, the data do not allow us to disentangle these two hypotheses, but we provide recommendations that will enable researchers to do so. [ABSTRACT FROM AUTHOR]

A relevant number of reports have examined the role of airborne signals in plant-plant communication, indicating that volatile organic compounds (VOCs) can prime neighboring plants against pathogen and/or herbivore attacks. Conversely, there is very limited information available on the possibility of the emission of VOCs by emitter plants under abiotic stress conditions, which may alert neighboring unstressed plants and prime these individuals (receivers) against the same stressors. The present opinion paper briefly reviews a few reports examining the effect of infochemicals produced by emitters on receiver plants subjected to abiotic stresses typical of global climate change. The ecological implications of these dynamics, as well as some concerns related to the potential roles of inter-plant communication in environmentally controlled experiments, have arisen. Some possible inter-plant communications applications (biomonitoring and biostimulation), mediated by airborne signals, and some directions for future studies on this topic, are also provided.

Diverse ecologically important metabolites, such as allelochemicals, infochemicals and volatile organic chemicals, are involved in marine organismal interactions. Chemically mediated interactions between intra- and interspecific organisms can have a significant impact on community organization, population structure and ecosystem functioning. Advances in analytical techniques, microscopy and genomics are providing insights on the chemistry and functional roles of the metabolites involved in such interactions. This review highlights the targeted translational value of several marine chemical ecology-driven research studies and their impact on the sustainable discovery of novel therapeutic agents. These chemical ecology-based approaches include activated defense, allelochemicals arising from organismal interactions, spatio-temporal variations of allelochemicals and phylogeny-based approaches. In addition, innovative analytical techniques used in the mapping of surface metabolites as well as in metabolite translocation within marine holobionts are summarized. Chemical information related to the maintenance of the marine symbioses and biosyntheses of specialized compounds can be harnessed for biomedical applications, particularly in microbial fermentation and compound production. Furthermore, the impact of climate change on the chemical ecology of marine organisms—especially on the production, functionality and perception of allelochemicals—and its implications on drug discovery efforts will be presented.

Programmed cell death (PCD) in marine microalgae was suggested to be one of the mechanisms that facilitates bloom demise, yet its molecular components in phytoplankton are unknown. Phytoplankton are completely lacking any of the canonical components of PCD, such as caspases, but possess metacaspases. Metacaspases were shown to regulate PCD in plants and some protists, but their roles in algae and other organisms are still elusive. Here, we identified and biochemically characterized a type III metacaspase from the model diatom Phaeodactylum tricornutum, termed PtMCA-IIIc. Through expression of recombinant PtMCA-IIIc in E. coli, we revealed that PtMCA-IIIc exhibits a calcium-dependent protease activity, including auto-processing and cleavage after arginine. Similar metacaspase activity was detected in P. tricornutum cell extracts. PtMCA-IIIc overexpressing cells exhibited higher metacaspase activity, while CRISPR/Cas9-mediated knockout cells had decreased metacaspase activity compared to WT cells. Site-directed mutagenesis of cysteines that were predicted to form a disulfide bond decreased recombinant PtMCA-IIIc activity, suggesting its enhancement under oxidizing conditions. One of those cysteines was oxidized, detected in redox proteomics, specifically in response to lethal concentrations of hydrogen peroxide and a diatom derived aldehyde. Phylogenetic analysis revealed that this cysteine-pair is unique and widespread among diatom type III metacaspases. The characterization of a cell death associated protein in diatoms provides insights into the evolutionary origins of PCD and its ecological significance in algal bloom dynamics.

Programmed cell death (PCD) in marine microalgae was suggested to be one of the mechanisms that facilitates bloom demise, yet its molecular components in phytoplankton are unknown. Phytoplankton are completely lacking any of the canonical components of PCD, such as caspases, but possess metacaspases. Metacaspases were shown to regulate PCD in plants and some protists, but their roles in algae and other organisms are still elusive. Here, we identified and biochemically characterized a type III metacaspase from the model diatom Phaeodactylum tricornutum , termed PtMCA-IIIc. Through expression of recombinant PtMCA-IIIc in E. coli , we revealed that PtMCA-IIIc exhibits a calcium-dependent protease activity, including auto-processing and cleavage after arginine. Similar metacaspase activity was detected in P. tricornutum cell extracts. PtMCA-IIIc overexpressing cells exhibited higher metacaspase activity, while CRISPR/Cas9-mediated knockout cells had decreased metacaspase activity compared to WT cells. Site-directed mutagenesis of cysteines that were predicted to form a disulfide bond decreased recombinant PtMCA-IIIc activity, suggesting its enhancement under oxidizing conditions. One of those cysteines was oxidized, detected in redox proteomics, specifically in response to lethal concentrations of hydrogen peroxide and a diatom derived aldehyde. Phylogenetic analysis revealed that this cysteine-pair is unique and widespread among diatom type III metacaspases. The characterization of a cell death associated protein in diatoms provides insights into the evolutionary origins of PCD and its ecological significance in algal bloom dynamics. [ABSTRACT FROM AUTHOR]

Aphis gossypii Glover (Hemiptera: Aphididae) is an important cucumber pest especially in greenhouse. The efficacy of simultaneous release of generalist predator, Orius albidipennis Reuter (Hemiptera: Anthocoridae) and a specialist parasitic wasp, Aphidius colemani Viereck (Hymenoptera: Braconidae), was evaluated in laboratory conditions against the pest. For this purpose, investigations were carried out on preference of the predator between parasitized and non-parasitized aphids. In addition, production of volatile infochemicals between the natural enemies (NEs) was studied by olfactometry trials. In another part of this research, systemic production of volatile synomone by the infested cucumber plants for attraction of each NE was examined by the olfactometry tests. Results revealed that O. albidipennis had no obvious preference to either the parasitized or non-parasitized aphids, while both NEs were significantly attracted to volatiles emitted from infested host plants. Our findings revealed that each of the NEs avoided odors which indicated the presence of another intraguild competitor. The documented facts from the entire study reveal that the NEs are good biocontrol agents against A. gossypii on cucumber, but their avoidance from each other makes simultaneous release of the predator and parasitic wasps unsuitable for biological control of this aphid.

Chemical communication within an aquatic environment creates an intricate signaling web that provides species with information about their surroundings. Signaling molecules, like oxylipins, mediate a multitude of interactions between free-living members of a community including non-consumptive effects by predators. Parasites are another source of signaling molecules in aquatic communities and contribute directly by synthesizing them or indirectly by manipulating host chemical cues. If chemical cues of infected hosts are altered, then non-consumptive interactions between other members of the community may also be affected. Different cues from infected hosts may alter behaviors in other individuals related to foraging, competition, and defense priming. Here, we discuss how parasites could modify host chemical cues, which may have far reaching consequences for other community members and the ecosystem. We discuss how the modification of signaling molecules by parasites may also represent a mechanism for parasite-modified behavior within some systems and provide a mechanism for non-consumptive effects of parasites. Further, we propose a host-parasite system that could be used to investigate some key, unanswered questions regarding the relationship between chemical cues, parasite-modified behavior, and non-consumptive effects. We explain how trematode-gastropod systems can be used to test whether there are alterations in the diversity and amounts of signaling molecules available, and if habitat use, immune function, and behavior of other individuals and species are affected. Finally, we argue that changes to pathway crosstalk by parasites within communities may have broad ecological implications.

Keywords: chemical communication; insights; olfactory signaling; infochemicals; semiochemicals; Germany; intraspecific; interspecific; pheromones; sexual communication; parasitoids; neuroecology EN chemical communication insights olfactory signaling infochemicals semiochemicals Germany intraspecific interspecific pheromones sexual communication parasitoids neuroecology 286 288 3 03/22/22 20220401 NES 220401 The topics of insect chemical communication in this issue can be subdivided into intra- and interspecific signaling mechanisms. 22 Mair MM & Ruther J (2019) Chemical ecology of the parasitoid wasp genus Nasonia (Hymenoptera: Pteromalidae). Another identifies a parasitoid-derived mortality-inducing protein, and discusses its potential for biological pest control. Males of the parasitoid wasp I Muscidifurax raptorellus i Kogan & Legner (Hymenoptera: Pteromalidae) start their courtship of a potential female mating partner with conspicuous wing fanning behavior. [Extracted from the article]

Summary: Since the holobiont concept came into the limelight ten years ago, we have become aware that responses of holobionts to climate change stressors may be driven by shifts in the microbiota. However, the complex interactions underlying holobiont responses across aquatic and terrestrial ecosystems remain largely unresolved. One of the key factors driving these responses is the infochemical‐mediated communication in the holobiont. In order to come up with a holistic picture, in this Viewpoint we compare mechanisms and infochemicals in the rhizosphere of plants and the eco‐chemosphere of seaweeds in response to climate change stressors and other environmental stressors, including drought, warming and nutrient stress. Furthermore, we discuss the inclusion of chemical ecology concepts that are of crucial importance in driving holobiont survival, adaptation and/or holobiont breakdown. Infochemicals can thus be regarded as a 'missing link' in our understanding of holobiont response to climate change and should be investigated while investigating the responses of plant and seaweed holobionts to climate change. This will set the basis for improving our understanding of holobiont responses to climate change stressors across terrestrial and aquatic ecosystems. [ABSTRACT FROM AUTHOR]

One of the most studied and best-known mutualistic relationships between insects is that between ants and phloem-feeding insects. Ants feed on honeydew excreted by phloem-feeding insects and, in exchange, attack the phloem feeders’ natural enemies, including parasitic wasps. However, parasitic wasps are under selection to exploit information on hazards and avoid them. Here, we tested whether parasitic wasps detect the previous presence of ants attending colonies of phloem feeders. Behavioural assays demonstrate that wasps left colonies previously attended by ants more frequently than control colonies. This behaviour has a potential cost for the parasitic wasp as females inserted their ovipositor in fewer hosts per colony. In a further bioassay, wasps spent less time on papers impregnated with extracts of the ant cues than on control papers. Gas chromatography coupled with mass spectrometry analyses demonstrated that ants left a blend of cuticular hydrocarbons when they attended colonies of phloem feeders. These cuticular hydrocarbons are deposited passively when ants search for food. Overall, these results suggest, for the first time, that parasitic wasps of honeydew producers detect the previous presence of mutualistic ants through contact infochemicals. We anticipate such interactions to be widespread and to have implications in numerous ecosystems, as phloem feeders are usually tended by ants. [ABSTRACT FROM AUTHOR]

Ulva is a ubiquitous macroalgal genus of commercial interest. Integrated Multi-Trophic Aquaculture (IMTA) systems promise large-scale production of macroalgae due to their high productivity and environmental sustainability. Complex host–microbiome interactions play a decisive role in macroalgal development, especially in Ulva spp. due to algal growth- and morphogenesis-promoting factors released by associated bacteria. However, our current understanding of the microbial community assembly and structure in cultivated macroalgae is scant. We aimed to determine (i) to what extent IMTA settings influence the microbiome associated with U. rigida and its rearing water, (ii) to explore the dynamics of beneficial microbes to algal growth and development under IMTA settings, and (iii) to improve current knowledge of host–microbiome interactions. We examined the diversity and taxonomic composition of the prokaryotic communities associated with wild versus IMTA-grown Ulva rigida and surrounding seawater by using 16S rRNA gene amplicon sequencing. With 3141 Amplicon Sequence Variants (ASVs), the prokaryotic richness was, overall, higher in water than in association with U. rigida. Bacterial ASVs were more abundant in aquaculture water samples than water collected from the lagoon. The beta diversity analysis revealed distinct prokaryotic communities associated with Ulva collected in both aquacultures and coastal waters. Aquaculture samples (water and algae) shared 22% of ASVs, whereas natural, coastal lagoon samples only 9%. While cultivated Ulva selected 239 (8%) host-specific ASVs, wild specimens possessed more than twice host-specific ASVs (17%). Cultivated U. rigida specimens enriched the phyla Cyanobacteria, Planctomycetes, Verrucomicrobia, and Proteobacteria. Within the Gammaproteobacteria, while Glaciecola mostly dominated the microbiome in cultivated algae, the genus Granulosicoccus characterized both Ulva microbiomes. In both wild and IMTA settings, the phylum Bacteroidetes was more abundant in the bacterioplankton than in direct association with U. rigida. However, we observed that the Saprospiraceae family within this phylum was barely present in lagoon water but very abundant in aquaculture water. Aquaculture promoted the presence of known morphogenesis-inducing bacteria in water samples. Our study suggests that IMTA significantly shaped the structure and composition of the microbial community of the rearing water and cultivated U. rigida. Detailed analysis revealed the presence of previously undetected taxa associated with Ulva, possessing potentially unknown functional traits.

A relevant number of reports have examined the role of airborne signals in plant-plant communication, indicating that volatile organic compounds (VOCs) can prime neighboring plants against pathogen and/or herbivore attacks. Conversely, there is very limited information available on the possibility of the emission of VOCs by emitter plants under abiotic stress conditions, which may alert neighboring unstressed plants and prime these individuals (receivers) against the same stressors. The present opinion paper briefly reviews a few reports examining the effect of infochemicals produced by emitters on receiver plants subjected to abiotic stresses typical of global climate change. The ecological implications of these dynamics, as well as some concerns related to the potential roles of inter-plant communication in environmentally controlled experiments, have arisen. Some possible inter-plant communications applications (biomonitoring and biostimulation), mediated by airborne signals, and some directions for future studies on this topic, are also provided. [ABSTRACT FROM AUTHOR]

Vector control is an important component of the interventions aimed at mosquito‐borne disease control. Current and future mosquito control strategies are likely to rely largely on the understanding of the behavior of the vector, by exploiting mosquito biology and behavior, while using cost‐effective, carefully timed larvicidal and high‐impact, low‐volume adulticidal applications. Here we review the knowledge on the ecology of mosquito oviposition behavior with emphasis on the potential role of infochemicals in surveillance and control of mosquito‐borne diseases. A search of PubMed, Embase, Web of Science, Global Health Archive, and Google Scholar databases was conducted using the keywords mosquito, infochemical, pheromone, kairomone, allomone, synomone, apneumone, attractant, host‐seeking, and oviposition. Articles in English from 1974 to 2019 were reviewed to gain comprehensive understanding of current knowledge on infochemicals in mosquito resource‐searching behavior. Oviposition of many mosquito species is mediated by infochemicals that comprise pheromones, kairomones, synomones, allomones, and apneumones. The novel putative infochemicals that mediate oviposition in the mosquito subfamilies Anophelinae and Culicinae were identified. The role of infochemicals in surveillance and control of these and other mosquito tribes is discussed with respect to origin of the chemical cues and how these affect gravid mosquitoes. Oviposition attractants and deterrents can potentially be used for manipulation of mosquito behavior by making protected resources unsuitable for mosquitoes (push) while luring them towards attractive sources (pull). In this review, strategies of targeting breeding sites with environmentally friendly larvicides with the aim to develop appropriate trap‐and‐kill techniques are discussed. [ABSTRACT FROM AUTHOR]

Many species of parasitoid wasps use plant volatiles to locate their herbivorous hosts. These volatiles are reliable indicators of host presence when their emission in plants is induced by herbivory. Hyperparasitoids may also use information from lower trophic levels to locate their parasitoid hosts but little is known about the role of volatiles from the plant–host complex in the foraging behavior of hyperparasitoids. Here, we studied how Dendrocerus aphidum (Megaspilidae) responds to plant and host volatiles in a series of experiments. This hyperparasitoid uses aphid mummies as its host and hampers biological control of aphids by parasitoids in greenhouse horticulture. We found that D. aphidum females were strongly attracted to volatiles from mummy-infested sweet pepper plants, but only when clean air was offered as an alternative odor source in the Y-tube olfactometer. Hyperparasitoid females did not have a preference for mummy-infested plants when volatiles from aphid-infested or healthy pepper plants were presented as an alternative. These olfactory responses of D. aphidum were mostly independent of prior experience. Volatiles from the host itself were also highly attractive to D. aphidum, but again hyperparasitoid females only had a preference in the absence of plant volatiles. Our findings suggest that plant volatiles may confuse, rather than guide the foraging behavior of D. aphidum. Mummy hyperparasitoids, such as D. aphidum, can use a wide variety of mummies and are thus extreme generalists at the lower trophic levels, which may explain the limited role of (induced) plant volatiles in their host searching behavior. [ABSTRACT FROM AUTHOR]

The aim of the present study was to establish how a selection of herbivore-induced plant volatiles (HIPVs) regulate the behavioral response of Fopius arisanus. A total of ten HIPVs were selected which are major bioactive components produced by fruits immediately after being infested with eggs of Bactrocera dorsalis, a common pest parasitized by F. arisanus. The behavioral and electroantennogram (EAG) responses of both sexes of F. arisanus to these chemicals were investigated. Our results suggest that all tested HIPVs can elicit different levels of antennal and behavioral response for both sexes at a variety of concentrations. There were no significant differences in response levels between sexes for all compounds, except trans farnesol at a concentration of 10-2 ml/ml (v/v), indicating that it may be of value in biological control programs using F. arisanus. Furthermore, we observed that the behavioral and EAG dose-dependent curves of both sexes of F. arisanus could be largely divided into four types, namely steady decrease (ethyl octanoate, methyl octanoate, linalool, tetradecane, pentadecane), steady increase (trans farnesol), inverted V (cis-3-hexenyl acetate, β-myrcene, β-ocimene) and fluctuating (benzaldehyde). The ecological role of these HIPV components in the host location process of F. arisanus is discussed. [ABSTRACT FROM AUTHOR]

We live in the information age, but we still do not fully understand how the surrounding nature exchanges, collects, and manages information—both at the ecosystem and cellular levels. Still, it is crucial to possess a dynamic and developing comprehension of the functioning of nature in order to understand the phenomena occurring in our ever-changing world. Sometimes we encounter an attitude that there is no need to investigate anything further, as everything has already been researched. This is a very dangerous attitude. Without information, we should not actually talk about the age of information, and it is worth reviewing some knowledge that is deeply ingrained in us from time to time. Occasionally, it is worth taking a step back and considering whether we ourselves may have become trapped in dogmas that may hinder our understanding. This presentation focuses on various aspects of understanding nature, starting from single-celled organisms and ending with ecosystems. The topics that will be discussed among others are (1) infochemicals (how do they actually affect the biota?); (2) the remarkable process of cellular computation (does this imply that cellular materials can show a primitive intelligence?); and (3) the ability of plants to influence wind patterns and bring in more moisture from the ocean (what will happen to us when we excessively deforest?). [ABSTRACT FROM AUTHOR]

Cyanobacteria stand out among phytoplankton when they form massive blooms and produce toxins. Because cyanotoxin genes date to the origin of metazoans, the hypothesis that cyanotoxins function as a defense against herbivory is still debated. Although their primary cellular function might vary, these metabolites could have evolved as an anti-predator response. Here we evaluated the physiological and molecular responses of a saxitoxin-producing Raphidiopsis raciborskii to infochemicals released by the grazer Daphnia gessneri. Induced chemical defenses were evidenced in R. raciborskii as a significant increase in the transcription level of sxt genes, followed by an increase in saxitoxin content when exposed to predator cues. Moreover, cyanobacterial growth decreased, and no significant effects on photosynthesis or morphology were observed. Overall, the induced defense response was accompanied by a trade-off between toxin production and growth. These results shed light on the mechanisms underlying zooplankton–cyanobacteria interactions in aquatic food webs. The widespread occurrence of the cyanobacterium R. raciborskii in freshwater bodies has been attributed to its phenotypic plasticity. Assessing the potential of this species to thrive over interaction filters such as zooplankton grazing pressure can enhance our understanding of its adaptive success.

The dinoflagellate Symbiodinium sp. establishes symbiotic relationships with the anemone Exaiptasia diaphana Rapp. The process that leads to the reciprocal recognition of the two symbiotic partners is still not very well understood. We hypothesize that chemical signals are exchanged between the Exaiptasia diaphana-Symbiodinium holosymbiont and aposymbiotic anemones or between free living Symbiodinium and holo- and aposymbiotic Exaiptasia, leading to changes in organic and elemental compositions in the aposymbiotic anemones. In order to test these hypotheses, bleached anemones were exposed to the presence of either free living Symbiodinium, previously extracted from the same Exaiptasia clone, or to holobionts. The ex-hospite algae and the holobionts were included in dialyses membranes with a cut-off of 14 000 Da. In the control treatments, the experimental samples were exposed to the presence of empty dialysis tubes. The organic composition and the elemental composition of the anemones were determined by Fourier Transform Infrared Spectroscopy and Total Reflection X-Ray Fluorescence Spectroscopy/Gas Chromatography, respectively. The fact that both the organic and elemental composition of the experimental aposymbiotic anemones differed significantly from the controls, in the absence of any obvious nutritional effect, is suggestive of an exchange of chemical signals between the aposymbiotic and holosymbiotic anemones. [ABSTRACT FROM AUTHOR]

Chemical signalling is widespread across animal taxa. Even birds, once thought to have little or no sense of smell, are now known to possess a fully functional olfactory system and may thus respond to conspecific and heterospecific chemical signals. In birds, body odour derives primarily from preen oil, a complex chemical mixture that is potentially rich in information: for example, preen oil chemical composition differs between the sexes and among species. Hypothesizing that songbirds attend to preen oil odour cues in the contexts of intra- and interspecific communication, we presented breeding-condition adult song sparrows, Melospiza melodia , with preen oil odour cues in two-choice tests. We compared time spent in a Y-maze arm scented with preen oil from same-sex conspecifics relative to the absence of such odour; from opposite-sex relative to same-sex conspecifics; and from female brown-headed cowbirds, Molothrus ater (frequent brood parasites of song sparrows), relative to the absence of such odour. The time spent with same-sex conspecific preen oil was not significantly different than time spent without odour. However, both males and females spent more time with opposite-sex than same-sex preen oil. We found a sex-by-stimulus interaction with respect to female cowbird odour: male song sparrows spent more time with cowbird preen oil than without odour, but female song sparrows showed the opposite pattern. Our findings show that even relatively nonsocial species can attend to the information contained in preen oil secretions. • Songbird preen oil chemical composition differs between species and sexes. • Song sparrows spent more time with opposite-sex than same-sex conspecific odour. • Males spent more time with female cowbird odour while females did the opposite. • Even relatively nonsocial species attend to information in preen oil secretions. [ABSTRACT FROM AUTHOR]

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The interactions between two natural enemies (NEs) were studied in a tritrophic system to evaluate the efficacy of simultaneous releases of a parasitoid, Lysiphlebus fabarum Marshal (Hymenoptera: Braconidae) and a predator, Orius albidipennis Reuter (Heteroptera: Anthocoridae) against Aphis fabae Scopoli (Homoptera: Aphididae). Three experiments were performed to evaluate the prey preference of a predator to parasitized versus unparasitized aphid hosts; to investigate the emission of volatile synomones by the host plant, Vicia fabae , and to determine its behavioral effect on the NEs; and to determine behavioral effect of volatile infochemicals between NEs. Results showed that the female predatory bug did not show significant preference between parasitized and unparasitized aphids, but the male bug had significant preference for parasitized mummies. Olfactometry trials documented that both NEs were significantly attracted to volatile cues released by the host plant infested with the aphid. Each of the NEs avoided odors which indicated the presence of another intraguild competitor. Therefore, simultaneously releases of the NEs are not recommended. Unlabelled Image • There is intraguild predation between Orius albidipnnis and Lysiphlebus fabarum. • The natural enemies were attracted to volatile cues released by infested broad bean. • Each of the natural enemies avoided odors which indicated the presence of another intraguild competitor. • Simultaneously releases of the natural enemies are recommended. [ABSTRACT FROM AUTHOR]